This invention relates to a viewing screen combining high efficiency and uniformity of illumination with predetermined scattering characteristics, and particularly to such a screen formed through interference techniques.
In rear projection systems such as slide viewers and microfilm readers, an image is generally projected onto a diffusing screen where it is presented to the observer. Such a rear projection screen is generally viewed near the axis of the system. The diffusing screen should scatter the largest possible fraction of the light towards the observer, i.e., have a high efficiency, thereby requiring a smaller quantity of illumination. The screen must scatter the light not only with high efficiency, but also in such a manner that the intensity of the light reaching the observer from various points on the screen is as uniform as possible, i.e., have predetermined scattering characteristics. Conventional screens, e.g., ground glass, do not scatter the light as desired. Often, conventional screens have the further disadvantage of allowing a hot spot to appear near the center of the screen, causing difficulty to the observer. It would therefore be desirable to develop a screen capable of overcoming the disadvantages of the prior art.